Alterations in adipose tissue metabolism are being studied in obese subjects before and after weight reduction. At each weight, subjects are fed diets with different levels of carbohydrate. Rates of lipolysis and esterification as well as the mechanism of esterification are studied. The effect of glycerol released from adipose tissue on the regulation of food intake is being observed. In the same subjects, hypothalamic function as measured by the changes in level of peptide hormones in response to releaser hormones or insulin-hypoglycemia are measured. An immuno-assay for cholecystokinin is being developed for use in the same type of subject populations.